Why do coaches keep reminding golf and tennis athletes to concentrate on a good follow-through? It really should not matter that is done after the moment of contact with the ball. But it does. Howard and others show how, in a paper (citation below) on the effect of follow-through on learning and execution.
The details of motor control of an action (the details and timing of muscle commands) are held in memory as motor programs or motor memories. The appropriate motor memory must be learned and it must be retrieved from memory to be used. If we think of what happens just before and just after the important moment in an action, we have three things that can vary (lead-in - main-action - follow-through). Each different lead-in and each different follow-through would produce a different motor memory. So if there is only one lead-in and one follow-through there needs to be only one motor memory. All the practice in learning the skill can be concentrated in one motor memory. This results in faster, more accurate execution. If there are different actions near the main-action in time, those differences will give separate motor memories; and, if there are unrelated actions by in other parts of the body during the main-action, those too will give separate motor memories. The fewer similar motor memories the better.
“Although we have shown that consistent follow-through leads to faster learning through selection of a single memory, this does not preclude other potential advantages of the follow-through, such as injury reduction or other biomechanical advantages … Our findings suggest that distinct follow-throughs associated with different motor skills, such as different tennis strokes, will help maintain these skills in separate motor memories, thereby protecting them from interference when learning other skills. Moreover, even for a single skill, maintaining a consistent follow-through will speed up learning. An intriguing question is why a particular follow-through might be preferred when learning a skill. Our results suggest that variability in the follow-through, which might arise from planning variability, motor noise, or other sources of variability, would lead to a reduction in the speed of skill acquisition. Therefore, it may be optimal to choose the follow-through for a skill that can be executed with the minimum variability.”
Here is the paper’s abstract: “In ball sports, we are taught to follow through, despite the inability of events after contact or release to influence the outcome. Here we show that the specific motor memory active at any given moment critically depends on the movement that will be made in the near future. We demonstrate that associating a different follow-through movement with two motor skills that normally interfere allows them to be learned simultaneously, suggesting that distinct future actions activate separate motor memories. This implies that when learning a skill, a variable follow-through would activate multiple motor memories across practice, whereas a consistent follow-through would activate a single motor memory, resulting in faster learning. We confirm this prediction and show that such follow-through effects influence adaptation over time periods associated with real-world skill learning. Overall, our results indicate that movements made in the immediate future influence the current active motor memory. This suggests that there is a critical time period both before and after the current movement that determines motor memory activation and controls learning.”
Howard, I., Wolpert, D., & Franklin, D. (2015). The Value of the Follow-Through Derives from Motor Learning Depending on Future Actions Current Biology, 25 (3), 397-401 DOI: 10.1016/j.cub.2014.12.037